Just got a 2011 Mac Mini, the cheap one, and downloaded the Server App.
My local tech support (my Nephew) was NOT happy about Lion Server.... wanted to UPGRADE to 10.6 To be honest, I can see why, it has so many bugs I was regretting the download of 10.7 server.
Being impatient and not wanting to go thru the hassle of changing OS's, I just started dinking around. Note, I'm just home user, I'm fairly tech saavy, fairly new to MAC, I know nothing about servers. We have to two MBPs and this new mini, that's it. I just wanted faster backups, fast storage for music and other stuff, and that's about it.
SOLUTION: From the Server App, I simply clicked Time Machine, turned it on, and told it what drive to use... BOOM, I'm done, that's it! All I had to do was point my MBP to that drive an starting the MBP TimeMachine. Its that easy. Wow, really!
OTHER THOUGHTS:
I have a 4TB WD RAID (2 TB RAID 1). Its Firewire 800, so reasonable fast, and literally 6X cheaper than the equivalent Thunderbolt Promise drive (take a hike). My only concern is the Server puts all the client Time Machines in one partition... Now I have to figure out how to resize it. It blows me away a "server" doesn't have tools to resize a partition. Guess I'll have to load iPartition.
I was using a the same drive on the USB port of the Airport extreme. It was DOG slow! But it worked and is probably the cheapest network time machine setup you can have. Now, for 650 more, I have 100Mb backups and a cool new toy to play with. I'm probably going to upgrade my switch to gigabit. Then I'll have braggin rights over any other house on the block.